1. Field of the Invention
The present invention relates generally to equipment used in semiconductor processing. More particularly, the present invention relates to an extreme ultraviolet lithography system in which hoses which provide coolant to and from a heat exchanger are vibrationally isolated from the heat exchanger.
2. Description of the Related Art
Extreme ultraviolet (EUV) lithography is a semiconductor fabrication technology which enables semiconductors with small features, e.g., features with dimensions of approximately 45 nanometers (nm) or less, to be produced. In EUV lithography, a laser may heat xenon gas to create a plasma, although there are other methods used to make EUV plasmas. Electrons come off the plasma and radiate light. FIG. 1 is a block diagram representation of an EUV lithography system. An EUV lithography system 100 includes a vacuum chamber 128 which contains a source 104. Source 104 provides EUV light, and includes a plasma source 108 and a collector mirror 112 that reflects EUV light which come off of the plasma generated by plasma source 108 into an illuminator unit 116b of a body 116 of EUV lithography system 100. Illuminator unit 116b is a condenser that effectively collects light and directs or otherwise focuses the light onto a reticle 120. That is, illuminator unit 116b conditions light from plasma source 108 to improve uniformity. The light reflects off of reticle 120, through projection optics 116a of body 116, and onto a surface of a wafer 124.
Mirrors included in an EUV lithography system generally absorb some of light or radiation that enters the mirrors. Such mirrors (not shown) may be associated with illuminator unit 116b as well as with projection optics 116a. When light is absorbed by a mirror, the absorbed light is converted to heat. Heat generally causes distortion in the mirror, thereby degrading the optical performance of the mirror. When there is distortion in the mirror, the optical performance of the mirror is compromised.
The removal of heat from the mirrors is critical to ensure that an EUV lithography system performs with accuracy. When mirrors become heated, the mirrors may become distorted. The distortion of mirrors reduces the accuracy with which an EUV lithography system may perform. To prevent mirrors from becoming over heated, heat exchangers are often included in EUV lithography systems. In general, heat may be transferred from a mirror to a fluid associated with a heat exchanger. Cooled fluid is provided to the heat exchanger, and warmed fluid, i.e., the fluid into which heat is transferred from a mirror, is removed from the heat exchanger.
Hoses generally provide fluid, e.g., coolant, to a heat exchanger. Such hoses generally pass through a wall of a vacuum chamber. As leakage and outgassing associated with flexible hoses, e.g., rubber hoses, has an adverse effect on a vacuum environment associated with an EUV lithography system, stiff hoses, e.g., metal tubes, are often used to carry fluid to and from a heat exchanger. Stiff hoses, however, transmit vibrations associated with vacuum chamber walls to the heat exchanger and, hence, a mirror. Such vibrations may have an adverse effect on the overall performance of the EUV lithography system, particularly if the vibrations cause an illuminator unit, projection optics, a reticle, or a wafer to vibrate. By way of example, the accuracy of an EUV lithography process may be compromised when optics vibrate or are otherwise distorted.
While flexible hoses are less likely to carry vibrations associated with a wall of a vacuum chamber, flexible hoses have the adverse effect of outgassing and leaking. Stiff hoses generally do not outgas or leak, but may cause vibrations to be transferred to a mirror and other optical elements structurally connected to the mirror.
Therefore, what is needed is a method and a system which allows fluid to be provided to and carried from a heat exchanger that is arranged to provide cooling to a mirror of an EUV lithography system substantially without the adverse effects of outgassing, leakage, and the transfer of vibrations. That is, what is desired is a method and a system which provides vibration isolation such that vibrations of a vacuum chamber wall are not transferred to a mirror and other optical elements when stiff hoses are used to provide fluid to and from a heat exchanger.